Position and direction determining system



Feb. 13,1940. l 1 NEUFELD 2,190,038

POSITION AND DIRECTION DETERMINING SYSTFM Filed Jun e 25,l 1957 4 Sheets-Sheet 1 .I owok WOL Feb. 13, 1940. 1 .1. NEUFELD 2,190,038-

' POSITION AND DIRECTION DETERMINING SYSTFM.

Filed June 25, -195'7 4 Sheets-Sheet 2 CLE fici/Vie ,6410/0 @fc5/Vie FIGB INVENTOR Feb. 13, 1940. J. NEUFELD 2,190,038

` POSITION AND DIRECTION DETERMINING SYSTFM Filed June 25, 1957 4 sheets-sheet s INVENTOR gow-5b W3 Feb. 13, 1940. J; NEUFELD POSITION AND DIRECTION DETERMINING SYSTFM 4 Sheets-Sheet 4 Filed June 25, 1937 wlf Wax Patented Feb. 13, 1940 wenn POSITION AND DIRECTION DETERMINING SYSTEM l My invention relates to a device for Visually indicating the bearings of an aircraft in flight, and more particularly to a device conveying the information as to the linstantaneous position of the craft in the simplest possible manner.

In the arrangements-heretofore used the position finding required considerable manipulation by an operator in that he must first tune his direction finder to the station from which signals are received, turn his-loopvuntil no signal is received, determine the sense or direction, then repeat the same manipulations with 'regard to other transmitting stations,and from the information thus received to determine his geographical position.

It is an object of the present invention to obviate the inconveniences of the prior -art and to provide an improved method and apparatus that will indicate continuously the position of a craft 'go with respect to one or to a` plurality of transmitting stations. l

It is another object of the present invention to devise a reliable radio compass comprising a fixed directional aerial, that will operate automatically and indicate continuously the direction ci the course of the craft with regard to one or to a plurality of radio transmitting stations located on the territory above which the craft is dying.

it another object of my invention to' provide an arrangement including a map of the referred to territory and enabling the operator to determine instantly the position of the craft on the map from the directional indications of the course of the craft with regard to a plurality of lXed radio transmitting stations.

It is another object of my invention to devise a reliable radio compass comprising a xed directional aerial that will operate automatically 40 and indicate continuously and at `all times by visual indicating means the angular relationship between the course of the craft and the position oi the transmitting stationlto which the radio compass is tuned.

It is another object of my inventionto provide a navigational chart in combination with an automatic direction finder and a method of determining the vessels course and position on the navigational chart. 1

The novel features which Ibelieve to be' char.- acteristic of my invention are set .forth `with particuiarity in the appended claims. My invention itself, however, vboth as to its organization and method of operation, together with further ob- I jects and advantages thereof, will be .better `un- -the drawings, two directional antennae, l5 and regard to a` plurality of radio transmitting 10 stations.

Fig. 4 shows a-diagram explanatory to Eig. 3. Fig. 5 shows diagrammatically the position of the airplane with respect to three transmitting stations. y 15 Fig. 6 shows some geometrical relationships useful for `the understanding of the invention. Fig. 7 shows ysome angular relationships re,y ierring to the positionof a point with respec to three xed points.

Y Fig. 8 shows diagrammatically an electronic voitage divider whichconstitutes one of the elements in the arrangements shown inFig. l and in Fig. 3. f

My invention consists broadly in a method Aoi 425 determining angles of incidence of radiant 'energy l emanating from a plurality of single sources of radiation, comprising simultaneously receiving the signal energy from each source vby at least two separate and similar directional antennae 30 having their line of maximum and minimum receptivity in different directions, continuously and separately amplifying the received signals 'by lbalanced ampliers, continuously and sep- 'amplifiers and determining their ratio, and indicating the direction of each source of radiation as a function of theI said ratio.

Referring now more specifically to Fig. 1 of it, angularly displaced withrespect to each other, '-40 are xedly mounted'in any suitable manner on any desiredtype of craft. The antennae l5, l@ consist of loops Il and ,I3 respectively connected to non-directional antennae I9 and 2(1,tl1el ab-A sorbing power of rthe non-directional antennae being adjusted to produce the well known cardioid patterns.-

The loops are in such a position that a line -bisecting one of theangles formed by the intersec- A50 Ation 'of the planes of the loops is coincidentwith or parallel to the keel line ofthe vessel, and for each angular relation the loops shouldbe spaced so as to have no inductivereaction on each other.

Under such conditions yeach loop will absorb an 55k equal amount of signal energy emanating from a transmitting source, if the source is located on a line bisecting one of the angles formed by the two loops and will impress equal potentials upon their respective amplifiers.

Antennas I5 and Iii are connected to respective tuning systems 2|, 22 which, in turn, are coupled to radio receivers diagrarnmatically indicated by 23, 24, respectively, each radio receiver comprising means for obtaining tuned radio frequency amplification, detection and audio amplification. Radio receivers have a constant and equal inputoutput relationship over a wide range of input voltages. and 24 are respectively connected to a voltage dividing device 25. The latter is connected to an indicating meter 25.

The voltage dividing device 25 will be sub- -23 and 24.

The operation of the arrangement of Fig. 1 will be better understood if reference be made to Fig.

.2. Fig-2 represents the directionalresponsivity of antennasl and I5 in form of polar cardioid ,diagrams 2l and 28.

Assume now that the vessel is headed for .the radio beacon and the loops I1, I8 of the antennas .|5, I5 are symmetrically placed with respectA to v,the keel line.

Then the antennas will absorb equal amounts of signal energy. In Fig. 2 the amount of energy absorbed by the antenna I5 will be represented by the segment ab in the cardioid pattern 2 and the amount ofenergy absorbed by theantenna I5 will be equally repre- "sented by the same segment ab in the cardioid pattern 28. The receivers A23 and 2,4 respectively vconnected to the antennas I5, IG, will consequently deliver equal voltages to the electronic divider 25 and the `output of the electronic divider will indicate at the meter 26 the value ofthe ratio equal to one.

Y It is obvious that with the arrangement as described, the responsiveness of the two antennas 'remains equal as long as the airplane is headed directly forward or away from the stationr and` the value of the ratio indicated by 2E will be one.-

If the airplane veers away from the heading,

there is an increase in responsiveness in one of the antennas and a corresponding decrease -in the other antenna. In that connection it is important to note that the ratio of responsiveness of the two antennas remains constant for any given bearing, irrespective of the signal strength or distance from the station. Thispermits cali- 'brating the instrument dial 26 in degreesan important feature of the present invention. A

vnavigator will thus be instantaneously and autostation.

An additional and important feature of my invention consists in providing three or more radio compasses of the type shown in Fig. l, tuning each of the radio Compasses to a different A'frequency and thus providing three separate in dications giving the direction of the course with The output circuits of the receivers 23l reference to three different radio transmitting stations. By means of these indications and with the aid of an appropriate navigational chart it is possible to determine instantaneously the position of the craft in a manner that shall be explained hereafter.

Fig. 3 represents another embodiment of my invention comprising one antenna system connected to three separate tuning arrangements and adapted to produce angular indications in degrees of the course of the airplane with respect to three fixed radio transmitting stations.

Referring now more particularly to this gure, A is the input unitof the apparatus and coma v prises the directional antenna system and the switching arrangement. B1, B2, Bs are radio re- `ceivers tuned to frequencies f1, f2, f3 respectively and used for amplifying and detecting the said frequencies received on the loop antenna. C1, C2,

C3 are switching arrangements synchronized with the 'inputV unit A. D1, D2, D3 are electronic voltage dividersrespectively connected to C1, C2, C3. lVIi, M2, M3 are` indicators showing angular position of the airplane course with respect to the stations transmitting the signal frequencies f1, f2, fs. thesynchronizing unit and supplies synchronizing voltage to the switching arrangements in A, C1, C2,C3. 4 Y

Referring to A, loop antenna 30 is connected at each terminal through blocking condensers 3| land 3,2,to three electrode tubes 33, 34, the la- .ments o-f which are' connected together and grounded. Two equal alternating voltages, of the same frequency but opposite in phase, are applied from ground to the grids of 33 and 34 throughv equal radio frequency inductors 35, 35. Consequently when a positive voltage is applied to the grid of 33, a negative voltage is applied to the grid of 34 andk vice versa. It is well known that when a positive voltage is applied to the grid of a suitable thermionic device, the resistance of that device is relatively low, but when a negative voltage is applied to the grid its resistance is .relatively high. For this reason the ground is effectively placed at each end of the loop antenna alternately, once for each cycle of the alternating -voltages supplied by the synchronizing unit F.

The voltage developed by the loop antenna is applied simultaneously to the radio receivers B1,

The units B1, B2, B3 may be radio receivers of the usual type. comprising essentially a tuning ele- Ament, a radio frequency amplifier, a detector, and an audio amplier.

The circuit arrangements of C1, C2 and Ca are 5,

similar one to another and consequently only the one shownin C1 will be explained hereafter.

` Referring now more particularly to the circuit arrangement C1, it Contains two equal capacitors 438, 39, one terminal of each being connected to fthe output-of the radio receiver B1 and the other ,terminal .of each connected to anodes of therm- Vionic tubes 4U and 4I respectively, which pass current only when a positive voltage is applied to the grid.y TheV cathodesof and 4I are connected Fis i :.Bz, B3 tuned respectively to frequencies f1, fz, f3.

grid of 4i and vice versa, 'so that during one-half cycle of the applied alternating voltage the tube is conductive while during the other half cycle the tube 4l is conductive. The switching arrangement by means of which the tubes 40 and 4l become intermittently conductive may be readily synchronized with input unit A by applying as its `low-frequency alternating voltage the saine voltage that is applied to unit A. Unit F accomplishes this.

The operation of the arrangement will be eX- plained in connection with Fig. 4 representing two cardioid-patterns one of the said patterns corresponding to-the antenna 3B grounded by means of tube and the other pattern correspending to the antenna 3i! grounded by means of tube 34. The meansl of accomplishing this is shown in Fig. 3 in which the positive voltage from the synchronizing unit F is applied to the grid ci the tube negative voltage is applied to the grid of the tube 34. Then 33 draws current and has low resistance to ground, and S is cut on with high resistance to ground. When the phase of the app-lied voltage reverses, 33 is cut off and 3i draws current, and the grounding point of the loop. antenna is reversed about its center point.

Thus the iield pattern of the loop antenna is direction indicated by the arrow 52, the voltageI induced in the loop antenna will be the same for each pattern and indicated by the segment cd. Consequently the ratio of signals corresponding to leach pattern will be one.

It is obvious that the strength of the signals may vary with the distance between the airplane and the transmitter but their ratio will'be always equa-l to unity as long as the signal will come from the direction 52.

If, however, the `signal comes from another direction such as indicated by the arrow 53, the voltage received by the loop antenna for pattern 5i wiil be cgi which is greater than for pattern Sil namely, egg, and the ratio of the signals cgi/cya will have a certain determined value largerthan one. It is also obvious that this ratio of responeivencss will remain constant for the given'directicn 53 and independent of the signal strength or distance from the station.

Thus, if means be secured for measuring the reiative intensity of these two signals, and determining their ratio, not only can the direction ci' the transmitting station be determined but also the angular deviation `of the line of flight i the airplane from the direction of the transmitting station.

Remembering that when the tube 33 is conductive one loop antenna eld pattern is produced and at the same time the tube ll is conducgrounded at one end, for instance at 33, the sig-` nal at the output of kthe radio receiver B, is proportional to the eld pattern for that condition. This signal is applied between the common point of the condensers 38, 39 and ground and causes a current to pass through the valve 40 (which is at this instant conductive) and through the resistor 42 to ground.

If however the loop antennafis grounded at the other end i. e. at 3G, the signal at the output of the radio receiver B is' proportional to that condition. This signal causes a current to pass through the valve 4| (which is now conductive) l and through the resistor d3 tov ground.

In such a manner there appear across the resistors 42 and i3 intermittent voltages which are substantially proportional to the signals induced in the antenna for the pattern 50 and for the pattern 5|. (See Fig. 4.)

The resistors i2 and 43 are shunted by the capacitors M, 45. The latter charge themselves by the voltage across the resistors 42, 43 then discharge themselves across these resistors. Consequently across the resistors 42 and Sfthere appear non-intermittent voltages which are respectively proportional to the intermittent currents passing through the tubes 4U, il respectively. The voltages taken from the resistors 42 and 43 respectively when applied to the electronic voltage divider D1 will produce across the output terminals of the electronic divider an indication corresponding to the ratio of the signals induced by the antenna for the pattern 5B and 'for the pattern 5l. (See Fig. 4.)

This indication is transmitted to .the measuring instrument M1 which shows directly in degrees the location of the signal transmitting station with respect to the course of the vessel.

The arrangements designated by B2, C2, DaMz and B3, C3, D3, M3, are substantially alike in their structural details and in operation to the arrangements indicated by B1, C1, Di, M1. It is-noted however that the radio receivers B1, B2, B3 are tuned to dilerent frequencies f1, f2, f3 and M1, M2, M3 give different indications, each of said indications corresponding to the position of a transmitting station having a frequency f1, f2, f3 respectively. v

It is therefore apparent that I have provided a system for automatically and continuously indicating the angular .deviation yof the course of the airplane with respect to'three iixed transmitting stations. y v Consider now Fig. 5 representing'a map ofthe localityl over which the airplane is flying. Let M, N, S designate the three xed radio `transmitting stations and P the location of the airplane and the arrow bthe direction' ofthe course of the airplane at a given moment. The airplane is provided with a radio compass substantially as the one shown in Fig. 3, and adapted to give the following three indications: (l) lthe angle 7M between the direction of the arrow br and the line PM; (2) the angle 'yN .between the direction of the arrow band the line PN; (3) the angle Iys between the direction of the arrow b and the line PS. The angles 7M, yN, 'ys may be counted positively in the clockwise direction in 4this example 'yN and ys are positive and IyM is negative. These angles are smaller than 180.

The values 7M, 7N, ys which are automatically indicated by the instrument enable to determine two angles: (l) the angle a=yNfyM which 1s subtended by the stations M and N (that is the angle MPN), and (2) the angle @tvs-7N which is subtended by the stations N and S, that is the angle NPS.

It is apparent that the angle-a or the angle does not fix the position of the airplane but gives a position'circle C.. or Cp as shown. This results froma proposition lwhich proves that in the arc AOB of any circle AOBC (Fig. 6) vall the angles AOB, AOB, AOB, etc., are equal to one another. Similarly, all the `angles on the other side of the chord AB, such as ACB, AC'B, etc.,fwill be yequal to one another but will not be equal to AOB unless AB be the diameter of the circle.

If therefore in Fig. 5 the angle a subtended by M and N be found to be 60, then the ship must If on the other hand the angle subtended by N and S is 65, then the ship must lie somewhere on the circumference of the circle passing through the points N, S, and P, this circle being such that any point on it is subtended by the points M and N at an angle of 65 or 180-65. Since the position of .the ship must lie on boththese circles, it will be an intersection P, the other intersection being the common `station N.

In accordance with the present arrangement the pilot has also before him a map of the territory over which he is flying and which indicates the angular relation of various geographical locations'withrespect to the Xed points M, N and S. The map is shown in Fig. 7 and comprises the three iixed reference points M, N, S a pattern of circles Cgi, Ca2, C,z3 etc. passing through the points M, N and a pattern of circles CB1, Cz, C53,

etc. passing through the points N, S. Each of the circles C1,' Ca2, etc. being such that any point on vits circumference is subtended by the points M and N at an angle a1, a2, etc. respectively, and each ofv the circles C51, C52, etc. being such that any point on its circumference is subtended by the points N- and S at an angle c1, z, etc., respectively. l

Any geographical location shown on the map coincides with'the intersection point of a circle Ca with a circle C and such a geographical location can be identified by the angular coordinates and For instance the location L1 shown in Fig. '7 has as angular coordinates on, 13a i. e. the point L1 is subtended by M and N at an angle 1, and by N and S at an angle ,63. In the same manner the angular coordinates of another location Lz are aaii. e. the point L2 is subtended by M andv N at an angle a3 and by N, Sv at an angle l.

On the other hand in order to identify a location having as angular coordinates the values a and the pilot has to refer to his map and to determine the point of intersection of the circles Ca with the circle C.

It is now'apparentvthat the present invention will enable the pilot to be aware of"his exact location at any instant during the flight.

' Consider now the electronic divider designated kby blocks 23 and 24 in Fig. 1 and by blocks DI, D2,

Fig.l 3 and that Fig. 8 refers only to one of the elements of Figs. land 3,-and namely to the electronic divider.

Brieily, in Fig. 8 numerals' IIDa, IIb and II Ia, I I Ib designate two` pairs of input terminals. and the numerals I3Ila,v I30b1designate the output terminals ofv an electronic divider. As stated above. an electronic divider is adapted to produce across its output terminals a voltage, `representing substantially the ratio of voltages, applied respectively across the input terminals IIIla, IIIlb and IIIa, IIIb. The inputterminals IIIla, IIIlbl are connected to a circuit consisting of a resistance II2 in series with a resistance H3. Ihe input terminals IIIa, IIIZ)` are connected to' a circuit consisting of a resistance I Ill in series with a circuit arrangement designated by a block II5, the said circuit arrangement comprising two three electrode tubes IIG and II'I connected in pushpull, two resistors IIS, II9 connected across the f anodes of the tubes Il, IIl respectively and a battery I2I3 inserted between the catho-des of the tubes IIB, III and the common terminal of the resistors IIS, II9 respectively. The terminal I2! of I I5 is connected directly to o-ne of the terminals of I I3 while the other terminal of I I3 and the terminal I 22 of I I5 are respectively connected to the input terminals I 23, IM of a D. C. amplier I25. The D. C. amplier 25 is of a push-pull type well known in the art. One of the output terminals of the amplifier |25 is connected to the cathodes of the tubes I I6,

battery |28 to the grids of the tubes I I6, i I1.

The operation of this arrangement can be eX- plained as follows:

Let R designate the resistance of II2 or IM,

' these two resistances being equal one to another minals I3Ila, I3Ilbcan be used for controlling the equivalent resistance r2 of the block IIE and the magnitude of this voltage determines the Value of the Iresistance r2.

The current owing from the terminal Ila into the resistor I I2 in, series with the resistor I I3 and. returning to the terminal IIIlb can be expressed as follows:

E y Z1= (l) Assuming that T1 R the expression (l) reduces to and the voltage across the terminals of the resistance II3 can be expressed as follows:

In a similar manner, the current owing from the terminal I I la into the resistor IIlI and traversing the block IIE from the terminal I22 to the terminal I2I and entering into the terminal I Ib can be expressed as follows:

III and the otherl voutput terminal of I is connected through the Zz=m (4) Assuming that r2 R the expression (4) reduces to The voltages 'v1 and c2 oppose each other in such a manner that the voltage m across the input terminals I23, |211 of the D. C. amplifier 25 is equal to the diiierence of 121 and o2 i. e.

1 v3 U1 712 ='[E17'1 Ezlz] (7) and the amplied voltage across the output tel'- minals ISa, i301) of the D. C. amplifier is K v4 Iws =T[Em Em] (8) where K is an amplication factor.

The voltage o4 in series with the voltage of the battery |28 constitutes the grid bias of the tubes I I6, I Il. It is apparent that v4 determines the plate resistance of the tubes and also determines the resistance r2 of the block H5. Under the conditions shown in the gure the value of T2 is such as to render the expression very small i. e.

Assume that the expression `(9) is zero, i. e.

It is thus seen from the formula (12) that the magnitude of the resistance T2 numerically eX- presses the ratio of the voltages El and E2. Consequently the problem of determining the ratio of voltages across the terminals IIIla, I-Ib and Ma., IIIb is equivalent to determining r2, i. e. the equivalent resistance of the block H5 between the terminals 12E and I22. On the other hand the value of r2 is controlledand determined by the voltage o4 across the output terminals Itc, i3d-b. Consequently in the expression (12)l instead of measuring the value T2 expressing the ratio :S1/E2 it is sufficient to determine the Voltage o4 which corresponds to the given value of frz, the said voltage or being measured across the output terminals I3a, |3011.

If now the relative values of the voltages E1 and E2 change the voltage across the output termina-ls ISM, I3Ilbwill indicate a new value of the ratio E1/E2 and, in general, in case of vary-A ing input voltages the voltage across the output terminals I3Ila, Iilb will indicate automatically and continuously the instantaneous value of their ratio.

lAssume for instance that the voltage E2 increases and the voltage E; is maintained con-v stant. Then the current i2 and the voltagevz will also increase, and will cause a corresponding variation of the voltage v3. Then the ampliiied voltage 'U4 derived from the output terminals of I25 changes `its value in such a manner as to cause a decrease of the resistance 1'2 of the block I I5. Then the voltage dr'op D2 across the resistor T2 becomes again substantially equal to the-voltage vdrop o1 across the resistor r1 so that the relation (10) is substantially satisfied. It `should be noted, however, that in this case the resistance r2 has a dierent and a smaller value which corresponds to a new and a smaller value oi" the Ell/E2'. To this new value of r2 correspondsthe new value of U4 which is directly indicated by the voltage across the output terminals I30a, |3012.

It is therefore apparent that the electrical circuit, substantially as shown and described in connection with Fig. 8 operates as an electronic divider and may be substituted in place of blocks 23 and 24 in Fig. 1 and in place of blocks D1, Dz, D3 in Fig. 3. f

In view of my invention and disclosure, variations and modications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain part or all of the benets of my invention without copying the structure shown, and I, therefore claim all such in so far as they fall within the reasonable spirit and scope of my invention.

I claim:

1. A radio direction finder for determining angle of incidence of a radio wave emanating from a single source of radiation, comprising two aerials, each of the said aerials consisting of a loop associated with a non-directional antenna, means for deriving. electrical signals impressed on each of said aerials by the rradio wave, and an electrical network responsive to the said signals to produce an electrical current, the mag.- nitude of which represents the quotient of magsenting the direction of the said radiowave.

2. A radio direction finder for determining angle of incidence of a vradio wave emanating from a single source of radiation, comprising two aerials, means for deriving electrical signals impressed on each of said aerials by the lradio Wave, and an electrical network responsive tothe said `nitudes of the said signals, said quotient represignals to produce a current, the magnitude` of which indicates substantially the quotient of :the magnitudes of the said signals, the said quotient representing the angleoi` incidence of the said radio` wave.

3. In apparatus for guiding an aircraft in space the combination with a plurality of radio transmitting stations of an indicating means on said aircraft for automatically and continuously indicating the directions at which the said radio transmitting stations are located, said indicating means comprising at least two directional antennae, means for .continuously and simultaneously deriving electrical effects impressed on each of said antennae by each of the said radio transmitting stations, electrical means to automatically indicate auotients of magnitudes of the electrical eects, each quotient corresponding to two effects impressed on the two antennae and derived from one transmitting station, the said quotients representing directions at which the transmitting stations are located.

4. A radiojdirection finder for indicating the direction of a radio wave comprising apair of crossedv pick-up coils mounted ata predetermined angle with each other for receiving directionally the said wave and an electrical network connected to the said pick up coils for producing a current, the magnitude of which represents the quotient of the magnitudes of the signals derived from the said pick up coils, a meter for indicating the magnitude of the said current as a measure of the said direction.

5. The method of determining angle of incidence of a radio wave which consists in producing two electrical signals, each of the said signals depending upon the intensity of the said radio l wave, producingr an electrical current representing afunctional relationship between the intensities of the said signals, the said functional relationship depending upon the angle of incidence of the said radio wave and remaining constant when the strength of the said wave varies, and determining the intensity of the said current as a measure of the said angle of incidence.

6. The method of determining angle of incidence of a radio wave, which consists in receiving two components of the said radio wave with respect to two different directions, producing an electrical current representing a functional relationship between the magnitudes of the said components, the said functional relationship depending upon the direction of the said radio wave andremaining constant when the strength of the said wave varies, and determining the intensity of the said current as a measure of the said angle of incidence.

'7. The method of determining angle of incidence of a radio wave which consists in producing intermittently two electrical signals depending upon the direction and the intensity of the said radio-wave, and producing an electrical signal representing a functional relationship between the intensities of the said signals, the said functional relationship depending upon the angle of incidenceof the said radio wave and remaining constant when the strength of the said wave varies.

8. The method of indicating the direction'y from a point to a source of electromagnetic waves which includes generating by induction separate electric currents each of which has a fixed relation with the intensity of electromagnetic waves, amplifying said currents, producing from the said currents another electric current having a xed relation with the direction of the electromagnetic waves, and remaining constant when the intensity of said waves varies, and determining the direction from the said point to the said source as a measure of the strength of the said other electrical current.

9. The method of determining angle of incidence of a radio signal which comprises receiving two components of the said radio signal with respect to two differentdirections, producing an electrical current representing substantially the quotient of the magnitude corresponding to one of the said components divided by the magnitude corresponding to the other component and determining the intensity of the said current as a measure of the said angle of incidence.

10. In a method of determining the position of a craft in a radio-field the step which consists in collecting two electrical signals from the* said radio-eld and in producing an electrical current the magnitude of which represents substantially the quotient of the magnitude dependent upon one of the said electrical signals divided by the magnitude dependent upon the other electrical signal.

11. In a method of guiding a craft in a radioield the step which consists in collecting intermittently two electrical signals from the said radio-eld and in producing an electrical current representing substantially the quotient of the magnitude dependent upon one of the said electrical signals divided by the magnitude dependent upon the other electrical signal.

12. The method of determining angle of incidence oi radio signal which consists in receiving intermittently two components of the said signal with respect to two different directions and producing an electrical signal representing substantially the quotient of the magnitude corresponding to one of the said components divided by the magnitude corresponding to the other component.

13. In an apparatus for indicating angle of incidence of an incoming radio signal, means for receiving the said signal and for producing two electrical currents depending upon the said signal, an electrical network responsive to the said two currents for producing another electrical current the magnitude of the said other electrical current representing a functional relationship between the magnitudesof the first said currents, the said functional relationship depending upon the direction of the said incoming signal and remaining constant when the strength of this signal varies.

14. In an apparatus for indicating angle of incidence of a radio signal, means for receiving two components of the said radio signal with respect to two different directions and an electrical network for producing an electrical current the magnitude of which represents substantially the quotient of the magnitude corresponding to one of the said components divided by the magnitude corresponding to the other component.

15. An apparatus for determining the position of a craft in a radio-eld comprising means for collecting two electrical signals from the said radio-eld and an electrical network for producing an electrical current the magnitude of which represents substantially the quotient of the magnitude dependent upon one of the said electrical signals divided by the magnitude dependent upon the other electrical signal.

16. An apparatus for determining the position of a craft in a radio-eld comprising means for intermittently collecting two electrical signals from the said radio-field and Ameans for producing an electrical current representing substantially the quotient of the magnitude dependent upon one of the said electrical signals divided by the magnitude dependent upon the other electrical signal.

1'7. An arrangement for guiding a craft comprising a fixed radio-transmitting station cn ground and means located in the craft for producing intermittently two electrical signals dependent upon the radio-waves received from the said transmitting. station and a means,v located on the craft, for producing an electrical current representing substantially the quotient ci' the magnitude dependent upon one of the said electrical signals divided by the magnitude dependent upon the other electrical signal.

18. In an apparatus for determining angle oi incidence of a radio signal, an aerial, a switching arrangement in the said aerial, means for actuating the said switching arrangement to impart said signals corresponding respectively to the said two directional characteristics, means for proinduced in the said aerial, theducing an electrical current representing sub-y ,v

stantially the quotient of the magnitude dependent upon one of the magnitude depen the said signals divided by dent upon the other signal. 

